Chemical-mechanical polishing is a process utilized for removing materials during semiconductor device fabrication. A prior art method of chemical-mechanical polishing is described diagrammatically with reference to FIG. 1. Specifically, FIG. 1 illustrates a construction 10 comprising a semiconductor substrate 12, and a polishing pad 14 provided over substrate 12. Semiconductor substrate 12 can comprise, for example, monocrystalline silicon having one or more layers of insulative and/or conductive materials provided thereover. To aid in interpretation of the claims that follow, the terms “semiconductive substrate” and “semiconductor substrate” are defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above.
Substrate 12 can comprise a conductive layer comprising, consisting essentially of, or consisting of, copper (not shown) at an upper surface, and the polishing operation shown in FIG. 1 can be utilized to planarize such copper-containing material. Polishing pad 14 will typically comprise a porous polyurethane material. A slurry 15 is provided at an interface between pad 14 and substrate 12. Slurry 15 comprises particulates (such as, for example, silicon dioxide and/or aluminum oxide particles) in a liquid medium. The liquid can comprise, for example, water.
In operation, pad 14 is displaced relative to substrate 12, with such displacement indicated by arrow 16. It is to be understood that pad 14 can be displaced in a linear relation relative to substrate 12 (as indicated by arrow 16) and/or in a rotational relation relative to substrate 12. Also, it is to be understood that pad 14 can, in exemplary applications, be a round pad associated with a rotating platen in particular apparatuses, or can be a non-round pad associated with a web of material moved relative to substrate 12 in other apparatuses (with such other apparatusses frequently being referred to as web chemical-mechanical polishing tools). Also, it is to be understood that the displacement of pad 14 relative to substrate 12 can occur by movement of one or both of pad 14 and substrate 12.
Displacement of pad 14 relative to substrate 12 causes abrasion of the upper surface of substrate 12 with the material of slurry 15. Such abrasion polishes (typically planarizes) an upper surface of substrate 12. More specifically, pad 14 comprises a polishing surface 18 which contacts slurry 15 and causes abrasion of an upper surface of substrate 12 with slurry 15.
After polishing of the upper surface of substrate 12, the substrate is removed from proximate pad 14, and surface 18 is reconditioned. The reconditioning removes liquid and particles associated with slurry 15 from within pores of pad 14. The reconditioning can also remove material displaced from the surface of substrate 12 that has lodged within the pores of polishing surface 18 of pad 14.
The reconditioning of pad 14 typically comprises displacing polishing surface 18 across a conditioning stone to rub undesired materials from over surface 18, and thereby expose a new, clean polishing surface. A typical conditioning stone will be a diamond-impregnated material, with the diamond particles being very coarse (typically, from about 100 microns to about 200 microns in average cross-sectional size). Diamond is utilized because of its superior wear characteristics relative to other materials.
An exemplary prior art conditioning apparatus is described with reference to FIGS. 2 and 3. FIG. 2 illustrates a side-view of a conditioning apparatus 20, and FIG. 3 illustrates a front-view of the apparatus. Apparatus 20 comprises a pad holder 22 having a polishing pad 14 retained therein. The polishing surface 18 of pad 14 is exposed. Apparatus 20 further comprises a conditioning stone 24 retained within a conditioning stone holder 26. The conditioning stone holder is mounted in a motor/gimbal which is configured to displace stone 24 relative to pad 14. The displacement can be along a linear or rotating direction. Motor/gimbal assembly 28 is connected through an arm 30 to a motor 32. Various gears and belts (not shown) can extend from motor 32 through arm 30 to motor 28, and accordingly can drive motor/gimbal 28 to accomplish displacement of stone 24 relative to pad 14.
In operation, stone 24 has a surface 25 which contacts polishing surface 18, and abrades surface 18 to remove contaminants from the surface. The removal of the contaminants ultimately exposes a clean surface of pad 14. Typically, stone 24 removes a portion of pad 14 associated with surface 18 to remove contaminants and expose a fresh polishing surface of the pad.
Various difficulties can occur during the reconditioning of polishing pads with conditioning stones. For instance, some contaminants can be difficult to remove from a polishing pad during reconditioning, with particular difficult contaminants including metals, such as, for example, copper. Accordingly, it would be desirable to develop improved methods for reconditioning polishing pads.